Low availability of selenium, an essential human micronutrient, in Malawian soils is responsible for its deficiency among the country's population, a study has found.

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Researchers from Malawi, New Zealand and the United Kingdom sought to establish both whether selenium content in different Malawian soils affects the mineral content of food crops grown in them, and its ultimate influence on the status of human health.

Selenium is incorporated into proteins, creating selenoproteins that form part of the human immune system that keeps people healthy.

In a country where 12 per cent of people aged 15-49 years old have HIV, selenium deficiency can be associated with low CD4 count, disease progression and the risk of death, says Alexander Kalimbira, researcher and senior lecturer in human nutrition at the Lilongwe University of Agriculture and Natural Resources, Malawi.

"We analysed blood and urine samples of 120 women aged 18-50 years from Mzuzu in the north [of the country] and the Shire Valley Agricultural Development Divisions in the south," says Kalimbira, who was involved in the research.

The researchers found widespread selenium deficiency among the women, apparently resulting from unfavourable soil factors such as land degradation and poor farming practices such as cultivation along steep slopes where there are fewer plants.

They suggest that through existing fertiliser subsidy programmes in Malawi there is potential for a public health intervention to enrich inorganic fertilisers with selenium. They hope that through doing this its presence in the country's soil will lead to high intake by plants, and thus combat nationwide selenium deficiency.

Stacia Nording, a nutritionist and dietician at a Malawi based Never Ending Food, a permaculture and sustainable nutrition advocacy group, supports the researchers' recommendation to enrich Malawi's soil. However, she believes that this should be done organically.

According to Nording, it is possible to enrich soils with selenium through natural means. For example, she says, selenium can be sourced through mushrooms that feed on dead organic material rather than through fertiliser fortification.

Calestous Juma, professor of the Practice of International Development at the Harvard Kennedy School, United States, says: "The area of micronutrients in human health is starting to receive considerable attention and much of the research will need to be carried out locally. This means that African countries will have to start thinking more seriously about increasing research and fostering cooperation for such activities".

The research was published last month (12 March) in Scientific Reports, an open access journal published by Nature.